The present invention relates to vehicle safety restraint products and generally to a seat belt retractor having means for absorbing (dissipating) a certain amount of energy during a crash by changing the deformation characteristics of a deformable internal part and in so doing controlling permitted occupant forward motion.
Safety belt restraint systems (or sub-systems) are designed to meet separate and distinct safety criteria and performance standards. The performance of these systems is measured in terms of known, occupant injury performance standards such as head injury criteria (HIC) and chest acceleration. It is believed that a limit of the performance of prior systems as manifested by increased occupant chest acceleration and related chest loading, is the result of an effective increased stiffness afforded by the seat belt system working independently or in concert with the air bag system. These injury criteria and the potential for actual injury can be reduced by introducing into the seat belt safety system an energy management device which absorbs, i.e. dissipates, a certain amount of the energy produced in a vehicular crash or other emergency driving condition and in so doing lessens the amount of energy imparted to the occupant lessening the injury and in so doing providing a means of controlling the displacement of the occupant.
It is an object of the present invention to provide an improved occupant protection system and more specifically an energy absorbing retractor that is fully operative prior to and during at least a first and a secondary vehicle impact. A further object of the present invention is to provide a variable energy absorbing or dissipating mechanism internal to the retractor and one which can be varied in accordance with accident parameters.
The present invention comprises: an energy absorbing seat belt retractor comprising: a frame; a spool rotatably mounted relative to the frame. including a lock wheel having a plurality of lock teeth associated therewith and adapted to receive a seat belt thereabout. The retractor additionally includes first means for engaging and stopping the rotation of the spool if vehicle deceleration or the rate increase of seat belt extraction are above certain determinable levels. Second means are located within the spool which join the lock wheel to the spool for prohibiting relative movement therebetween below a threshold input force level generated in part by occupant load on the seat belt and for generating a controlled energy dissipating reaction force on the seat belt after the input force exceeds the threshold level to permit a controlled rotation of the spool and the controlled protraction of the seat belt from the spool during at least a first and a second collision.
In the preferred embodiment of the invention the spool includes an axle assembly having a movable nut and deformable bushing interior thereto for dissipating or absorbing energy as it moves and a means for varying the deformation characteristics of the bushing to vary the amount of energy absorbed or deformed as a function of certain accident parameters.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.